firewire: ohci: Turn remote DMA support into a module parameter

This makes it possible to debug kernel over FireWire without the need to
recompile it.

[Stefan R: changed description from "...0" to "...N"]

Cc: Dave Hansen <[e-mail]>
Signed-off-by: Lubomir Rintel <[e-mail]>
Signed-off-by: Stefan Richter <[e-mail]>

Documentation/debugging-via-ohci1394.txt

···
 
 The firewire-ohci driver in drivers/firewire uses filtered physical
 DMA by default, which is more secure but not suitable for remote debugging.
-Compile the driver with CONFIG_FIREWIRE_OHCI_REMOTE_DMA (Kernel hacking menu:
-Remote debugging over FireWire with firewire-ohci) to get unfiltered physical
-DMA.
+Pass the remote_dma=1 parameter to the driver to get unfiltered physical DMA.
 
 Because the firewire-ohci driver depends on the PCI enumeration to be
 completed, an initialization routine which runs pretty early has been

drivers/firewire/ohci.c

···
 	", busReset events = "	__stringify(OHCI_PARAM_DEBUG_BUSRESETS)
 	", or a combination, or all = -1)");
 
+static bool param_remote_dma;
+module_param_named(remote_dma, param_remote_dma, bool, 0444);
+MODULE_PARM_DESC(remote_dma, "Enable unfiltered remote DMA (default = N)");
+
 static void log_irqs(struct fw_ohci *ohci, u32 evt)
 {
 	if (likely(!(param_debug &
···
 			  be32_to_cpu(ohci->next_header));
 	}
 
-#ifdef CONFIG_FIREWIRE_OHCI_REMOTE_DMA
-	reg_write(ohci, OHCI1394_PhyReqFilterHiSet, ~0);
-	reg_write(ohci, OHCI1394_PhyReqFilterLoSet, ~0);
-#endif
+	if (param_remote_dma) {
+		reg_write(ohci, OHCI1394_PhyReqFilterHiSet, ~0);
+		reg_write(ohci, OHCI1394_PhyReqFilterLoSet, ~0);
+	}
 
 	spin_unlock_irq(&ohci->lock);
 
···
 static int ohci_enable_phys_dma(struct fw_card *card,
 				int node_id, int generation)
 {
-#ifdef CONFIG_FIREWIRE_OHCI_REMOTE_DMA
-	return 0;
-#else
 	struct fw_ohci *ohci = fw_ohci(card);
 	unsigned long flags;
 	int n, ret = 0;
+
+	if (param_remote_dma)
+		return 0;
 
 	/*
 	 * FIXME:  Make sure this bitmask is cleared when we clear the busReset
···
 	spin_unlock_irqrestore(&ohci->lock, flags);
 
 	return ret;
-#endif /* CONFIG_FIREWIRE_OHCI_REMOTE_DMA */
 }
 
 static u32 ohci_read_csr(struct fw_card *card, int csr_offset)

lib/Kconfig.debug

···
 
 	  See Documentation/debugging-via-ohci1394.txt for more information.
 
-config FIREWIRE_OHCI_REMOTE_DMA
-	bool "Remote debugging over FireWire with firewire-ohci"
-	depends on FIREWIRE_OHCI
-	help
-	  This option lets you use the FireWire bus for remote debugging
-	  with help of the firewire-ohci driver. It enables unfiltered
-	  remote DMA in firewire-ohci.
-	  See Documentation/debugging-via-ohci1394.txt for more information.
-
-	  If unsure, say N.
-
 config BUILD_DOCSRC
 	bool "Build targets in Documentation/ tree"
 	depends on HEADERS_CHECK